In many types of fluid handling conditions it is highly important that means be provided for closing fluid flow in the event of an emergency. Valves exist on the market today which can be manually or mechanically closed upon demand; however, most require an externally supplied operating force to move the valve from the open to closed position. In many emergency situations the externally applied operating force may be impaired. An example of flow conditions which require the use of a safety valve is that of loading and unloading tanks, including the holds of tankers or barges, used for transporting petroleum products. During filling or delivery operations, if the line breaks, the vessel overflows, or if there is a fire, explosion, or other circumstance, it is important that means be provided for immediately closing fluid flow lines without depending upon the availability of an externally supplied motivating force.
The present invention is directed towards a valve of the type which, in one embodiment, is normally closed and which, in the absence of externally supplied motivating force, remains closed or, if opened, immediately moves to the closed position. The valve to be described herein includes an arrangement wherein it is normally closed against fluid flow. In order to open the valve, a positive fluid pressure must be applied to the valve. The valve will remain open as long as this externally supplied fluid pressure is available. In the event of an emergency, this externally supplied fluid pressure may be removed by automatic means, or in the event of an explosion, fire, or other catastrophe which destroys operating controls, the removal of the externally supplied hydraulic pressure will cause the valve to close. In other words, the valve is fail-safe and is closed at all times except in the presence of a positively supplied actuating fluid pressure signal to maintain the valve in an open position.
It is therefore an object of this invention to provide an improved safety valve. More particularly, an object of this invention is to provide an improved safety valve which provides automatic, fool-proof, and quick-acting shut-off of fluid flow, the valve being arranged in a manner to immediately move to the closed position and maintain a closed position in the absence of an externally supplied actuating fluid pressure signal.
These general objects, as well as other and more specific objects of the invention, will be fulfilled in the following description and claims, taken in conjunction with the attached drawings.